The Baltimore Sun's Orioles beat writer Eduardo A. Encina reports on the latest news on the Orioles from Boston, Massachusetts. (Kevin Richardson/The Baltimore Sun video)

BOSTON -- The Orioles traded veteran reliever Luis Ayala to the Atlanta Braves on Wednesday, receiving minor league left-handed reliever Chris Jones in return. But the move was less about unloading Ayala than it was allowing the Orioles the opportunity to keep Rule 5 pick T.J. McFarland while moving to a seven-man bullpen.

It lets the team go to back a four-man bench after playing short-handed since Saturday. The Orioles purchased the contract of outfielder Chris Dickerson from Triple-A Norfolk, and he replaced Ayala on the 40-man and 25-man rosters.

“The trade of Ayala allows us the opportunity to keep T.J. McFarland on our major league staff, someone who we like and would like to continue to develop,” Orioles executive vice president Dan Duquette said. “Chris Jones is on track to be a left-handed reliever in the big leagues.”

The trade also exposes the lack of maneuverability that existed within the Orioles bullpen. As a Rule 5 pick this winter, McFarland must stay on the roster for the entire season or the team likely loses him. And left-hander Brian Matusz and right-hander Darren O’Day — who recently signed a two-year extension and is solidified in a late-inning set-up role — are the only Orioles relievers with minor league options.

The Orioles couldn’t hold 13 pitchers — and have a short bench — for long. The team had been gauging other teams' interest in Ayala since the final weeks of spring training. Ayala also has a club-friendly $1 million option for 2013 that made him an attractive trade chip.

“Dan and I knew we didn’t want to do it very long and obviously we were on the same page with it,” Orioles manager Buck Showalter said of keeping 13 pitchers. “This is something that [didn’t happen] until we can get the right player back in the right deal where Luis was concerned, but we’ll see.

“T.J. is a 23-year-old left-handed pitcher,” Showalter added. “Who knows? He’s going to have to pitch and he’s going to have to have some success in order to keep him. We can’t just bury some guy. We like him. It wasn’t completely about keeping T.J. We liked the player we got back. We knew we weren’t going to be at 13 pitchers all year and following the off day we felt like it was a good time to go.”

McFarland, who would need to be offered back to the Cleveland Indians if he’s taken off the major league roster, threw 3 1/3 scoreless innings of relief in his big league debut Saturday.

“I still have to perform,” McFarland said. “The security is there a little bit, but not really because I still have to get outs. With the trade, it definitely bestows a little more confidence in me that they definitely are thinking more long-term to get rid of an option.”

The 35-year-old Ayala went 5-5 with a 2.64 ERA last season, but he allowed 44 percent of inherited runners to score.

“Luis did a nice job for us this year and last year,” Duquette said. “But we wanted to get down to 12 pitchers.”

Jones, a 15th-round draft pick of the Indians in 2007, was acquired by the Braves in the 2011 trade that sent Derek Lowe to Cleveland. Last season at Double-A Mississippi, Jones was 2-5 with a 3.90 ERA and 61 strikeouts and 69 hits in 60 innings.

Duquette said Jones made tremendous strides with his breaking ball and fastball last season at Double-A, improving his strikeouts-per-nine innings to 9.2 and his strikeout-to-walk ratio to 3.21, both career highs. Jones will report to Double-A Bowie.